In general in array antennas for satellite communications, a side-lobe level indicating the relative level, that is, relative signal strength, of a side lobe with respect to the main lobe is required to be low so as not to cause radio interference between satellite communication systems. Patent Literature 1 (Unexamined Japanese Patent Application Kokai Publication No. H9-214241) discloses an array antenna in which sub-arrays, each constituted by a plurality of antenna elements, are arrayed densely in a satellite orbital direction so that the side-lobe level is low.